An 82-year-old man presented with numbness and paresthesias in his genitals and saddle region, decreased sensation in his bladder and rectum and erectile dysfunction. In addition, he had several years of urinary urgency and with a diagnosis of enlarged prostate. MRI pelvis revealed a 5 cm expansile, permeative S1 vertebral body mass with soft tissue extension into the presacral space and S1 neural formina bilaterally causing mass effect on the S1 roots. Below are the cytology and histopathology of the sacral mass.

Figure 1: DQ 20x
Figure 2: DQ 60x
Figure 3: 40x pap
Figure 4: HE 20x

What is your diagnosis?

  • Metastatic adenocarcinoma
  • Chondrosarcoma
  • Conventional chordoma
  • Ecchordosis physaliphora

The correct answer is ...

Conventional chordoma.

Fine needle aspiration of the sacral mass demonstrates cellular smears with loosely cohesive groups and singly scattered epithelioid cells. These cells have a low nuclear to cytoplasmic ratio, abundant pale cytoplasm with vacuolations, mild nuclear size variation, conspicuous nucleoli. Binucleation and occasional large hyperchromatic cells were noted. Background showed mucinous/myxoid stromal material. Corresponding histological sections show nests and cords of polygonal cells with bland nuclei, pale eosinophilic cytoplasm with frequent cytoplasmic vacuolization (so-called physaliferous cells) infiltrating bone trabeculae. This morphology, in correlation with the strong positivity for pankeratin and brachyury and the imaging findings of a destructive sacral mass is characteristic of conventional chordoma.

There are several important differential diagnosis which should be excluded on the basis of morphology and immunophenotype. The groups of epithelioid cells with intracytoplasmic vacuolations and background myxoid stroma can mimic metastatic adenocarcinoma. In addition, the cells are positive for cytokeratins. However, brachyury positivity and radiological correlation will help in this distinction. The cytology, myxoid matrix and focal S100 positivity brings chondrosarcoma in the differential diagnosis. However, chondrosarcoma lacks cytokeratin and brachyury immunoreactivity and harbor IDH1/IDH2 mutations. In addition, imaging would show chondroid matrix in the mass lesion.

Lastly ecchordosis physaliphora (EP), represents a variant of a benign notochordal tumor that arises from the embryonic notochordal remnants. These lesions are usually small (less than 3 cm), and are incidental findings. These lesions are more common in clivus. Morphologically, they can look similar and will be brachyury positive. Therefore, distinction requires clinical and radiographic correlation.

Conventional chordoma is a malignant lytic, destructive lesion which arises in the bones of the axial skeleton (94 %), with a distribution of 32% at the skull-base, 32.8% in the mobile spine and 29.2% in the sacrum and coccyx. Extra-axial chordomas account for 6% of cases, occurring in other bones and soft tissue sites. Chordoma most commonly occur in the fifth to seventh decade of life. In the pediatric age group, speno- occipital region and cervical spine are commonly involved. As discussed above imaging findings show a lytic lesion with cortical destruction and a large soft tissue mass. The histological findings are characteristic of an infiltrating neoplasm with lobules of neoplastic cells separated by fibrous septi. The neoplastic cells are arranged in cords and nests in a pale myxoid background. The neoplastic cells have round nuclei with central nucleoli and eosinophilic to clear cytoplasm with prominent intracytoplasmic vacuolization (physaliphorous cells). By Immunohistochemistry, the neoplastic cells are diffusely positive for cytokeratin and variable positivity for S100. This malignant tumor recapitulates a notochordal phenotype of which it originates and has a hallmark expression of brachyury (encoded by TBXT gene), which shows nuclear immunoreactivity by IHC, as seen in this case. Recurrent mutations involving CDKN2A, LYST and TBXT (encodes brachyury) and mutations in epigenetic regulators and PI3K signaling such as PTEN have been identified. IDH1/IDH2 mutations are not present. The conventional chordomas are chemo resistant and are treated with wide surgical resection, with or without radiation therapy.

Figure 5: AE1_3 20x
Figure 6: Brachyury 20x


  1. McMaster ML, Goldstein AM, Bromley CM, Ishibe N, Parry DM. Chordoma: incidence and survival patterns in the United States, 1973-1995. Cancer Causes Control. 2001 Jan;12(1):1-11.
  2. Vujovic S, Henderson S, Presneau N, Odell E, Jacques TS, Tirabosco R, Boshoff C, Flanagan AM. Brachyury, a crucial regulator of notochordal development, is a novel biomarker for chordomas. J Pathol. 2006 Jun;209(2):157-65.
  3. WHO Classification of Tumors Editorial Board. Soft tissue and bone tumors. Lyon (France): International Agency for Research on Cancer; 2020. ( WHO classification of tumors series, 5th ed.; vol. 3).

Anna-Lee Clarke-Brodber, M.B.B.S.
Fellow, Cytopathology
Mayo Clinic

Judith Jebastin Thangaiah, M.B.B.S., M.D.
Senior Associate Consultant, Anatomic Pathology
Mayo Clinic

A 33-year-old woman with a prior history significant for a breast carcinoma nine years ago, presented with a palpable lump in her breast. Imaging showed a 0.7 x 0.6 x 0.3 cm oval hypoechoic mass with internal vascularity at 6 o’clock position, 4-5 cm away from the nipple, corresponding to the palpable area of concern.

Image 1: 10x
Image 2: 10x
Image 3: 20x
Image 4: 20x

Based on the prior clinical history and morphologic findings in the images above, what is the right diagnosis?

  • Apocrine carcinoma of the breast
  • Secretory carcinoma of the breast
  • Acinic cell carcinoma of the breast
  • Cystic hypersecretory hyperplasia of the breast

The correct answer is ...

Secretory carcinoma of the breast.

Secretory carcinomas of the breast are very rare. However, they are the most common primary pediatric breast malignancy. On histology, they show circumscribed margins, solid nests, cysts and gland formation with PAS+ intraluminal secretions. Tumor cells with abundant vacuolated or granular cytoplasm and low nuclear grade are seen. They are generally negative for estrogen receptor, progesterone receptor, and HER2 (triple negative). Most tumors have translocation yielding ETV6-NTRK3 fusion gene and are associated with a favorable prognosis in younger patients.

Apocrine carcinomas of the breast are rare tumors and comprise of up to 1% of all breast carcinomas. Tumor cells have distinct cell margins, abundant acidophilic cytoplasm with eosinophilic granules, central to eccentric vesicular nuclei with prominent nucleoli. They may also have glandular features with apocrine snouts. Apocrine carcinomas of the breast are typically negative for estrogen and progesterone receptors and can show expression for androgen receptor. HER2 positivity may be seen in one-third of apocrine carcinomas.

Primary acinic cell carcinomas are exceedingly rare in the breast and only a handful of cases have been reported in the medical literature. They are morphologically identical to their salivary gland counterparts and have a serous differentiation.

These carcinomas show diffuse infiltrative growth patterns of small glandular structures and are composed of cells with a coarse granular or clear cytoplasm resembling acinar cells of the salivary glands or Paneth cells. Although similar in some respects to secretory carcinoma, they lack its characteristic ETV6 gene rearrangement. Acinic cell carcinomas are usually triple negative and show expression for amylase and the granules are PAS positive diastase resistant.

Cystic hypersecretory hyperplasia can present as a palpable mass or occasionally can be asymptomatic. It is a benign lesion with good prognosis when not associated with atypia or carcinoma. Microscopically, cystically dilated ducts of various sizes with colloid-like material can be seen. Ducts are lined by flat, orderly, columnar epithelial cells with eosinophilic cytoplasm. The nuclei are bland, round or oval. They can be associated with pregnancy-like (pseudolactational) changes. Wide excision of the lesion is the recommended treatment for this lesion.


  1. Li D, Xiao X, Yang W, Shui R, Tu X, Lu H, Shi D. Secretory breast carcinoma: a clinicopathological and immunophenotypic study of 15 cases with a review of the literature. Mod Pathol. 2012 Apr;25(4):567-75. doi:10.1038/modpathol.2011.190. Epub 2011 Dec 9. PMID: 22157932.
  2. Hoda RS, Brogi E, Pareja F, Nanjangud G, Murray MP, Weigelt B, Reis-Filho JS, Wen HY. Secretory carcinoma of the breast: clinicopathologic profile of 14 cases emphasising distant metastatic potential. Histopathology. 2019 Aug;75(2):213-224. doi:10.1111/his.13879. Epub 2019 Jul 10. PMID: 31012486; PMCID: PMC6646069.
  3. Tanaka K, Imoto S, Wada N, Sakemura N, Hasebe K. Invasive apocrine carcinoma of the breast: clinicopathologic features of 57 patients. Breast J. 2008 Mar-Apr;14(2):164-8. doi: 10.1111/j.1524-4741.2007.00548.x. Epub 2008 Jan 31. PMID: 18248561.
  4. Pia-Foschini M, Reis-Filho JS, Eusebi V, Lakhani SR. Salivary gland-like tumours of the breast: surgical and molecular pathology. J Clin Pathol. 2003 Jul;56(7):497-506. doi: 10.1136/jcp.56.7.497. Erratum in: J Clin Pathol. 2003 Oct;56(10):804. PMID: 12835294; PMCID: PMC1769991.
  5. Shin SJ, Rosen PP. Pregnancy-like (pseudolactational) hyperplasia: a primary diagnosis in mammographically detected lesions of the breast and its relationship to cystic hypersecretory hyperplasia. Am J Surg Pathol. 2000 Dec;24(12):1670-4. doi: 10.1097/00000478-200012000-00012. PMID: 11117789.

Muhammad Ahmad, M.B.B.S.
Fellow, Multidisciplinary Breast Pathology
Mayo Clinic

Malvika Solanki, M.B.B.S., Ph.D.
Senior Associate Consultant, Anatomic Pathology
Mayo Clinic
Assistant Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science

A 30-year-old woman with history of developmental delay, cognitive disability, seizure disorder, and multiple renal masses, status post right partial nephrectomy for neoplasm, was evaluated for a newly found renal mass. CT showed a 2.2 cm enhancing mass in the left kidney. Fine needle aspiration and core biopsy of the new left kidney lesion were performed and the findings are shown on Figure 1.

Figure 1

In addition to this renal tumor, what other kidney neoplasm is this patient at risk for developing based on her genetic predisposition?

  • Clear cell renal cell carcinoma
  • Metanephric adenoma
  • Congenital mesoblastic nephroma
  • Angiomyolipoma

The correct answer is ...


Figure 1 shows cytology specimen (A, B) and biopsy (H&E, C, D) of a renal cell carcinoma with fibromyomatous stroma (previously known as Tuberous sclerosis-associated papillary RCC ). Histologically, this entity is characterized by elongated branching tubules or papillary structures composed of cells with distinct cell membrane, abundant clear cytoplasm, and prominent smooth muscle and fibromatous stroma (1). Immunohistochemical profile is characterized by reactivity to PAX8, CD10, CK7, CAIX (Fig.1 E,F), and molecular analysis revealed TSC/MTOR mutations but lack of VHL or chromosome 3p alterations. This neoplasm has indolent behavior.

Tuberous sclerosis complex (TSC) results from germline loss-of-function mutation in either TSC1 (9q24) or TSC2 (16p13). The majority of new cases are due to de novo mutations in TSC genes. It is inherited as autosomal dominant disease. Patients are at risk for renal cell neoplasms, which occur with female predominance and at younger age (2). Angiomyolipomas are one of the major features of TSC (3) and often occur as bilateral multifocal lesions (4,5). The most common types of renal cell carcinoma seen in patients with TSC include eosinophilic solid cystic renal cell carcinoma, renal cell carcinoma with fibromyomatous stroma, and hybrid oncocytic/chromophobe tumor (1).

Clear cell renal cell carcinoma is incorrect: Clear cell renal cell carcinoma is associated with von Hippel–Lindau disease.

Metanephric adenoma is incorrect: Metanephric adenoma consists of small, basophilic tubular epithelium arranged in tubules, glomeruloid structures, papillae, or exhibit solid growth pattern. It is positive for WT1 and CD57, and molecular studies reveal BRAF V600E mutation in up to 90% of the cases. These are often associated with polycythemia vera (6).

Congenital mesoblastic nephroma is incorrect: Congenital mesoblastic nephroma is the most common renal neoplasm diagnosed in infancy. Genetically it is characterized by trisomy 11 and t(12;15) leading to fusion of ETV6 and NTRK3 (7).


  1. Trpkov K, Williamson SR, Gill AJ, et al. Novel, emerging and provisional renal entities: The Genitourinary Pathology Society (GUPS) update on renal neoplasia. Mod Pathol. 2021 Jun;34(6):1167-1184. doi:10.1038/s41379-021-00737-6. Epub 2021 Feb 1. Erratum in: Mod Pathol. 2021 May;34(5):1037. PMID: 33526874.
  2. Henske EP, Cornejo KM, Wu CL. Renal Cell Carcinoma in Tuberous Sclerosis Complex. Genes (Basel). 2021 Oct 8;12(10):1585. doi:10.3390/genes12101585. PMID: 34680979; PMCID: PMC8535193.
  3. Trnka P, Kennedy SE. Renal tumors in tuberous sclerosis complex. Pediatr Nephrol. 2021 Jun;36(6):1427-1438. doi:10.1007/s00467-020-04775-1. Epub 2020 Oct 1. PMID: 33006051.
  4. Gupta S, Erickson LA. Tuberous Sclerosis-Associated Renal Neoplasm. Mayo Clin Proc. 2020 May;95(5):1089-1090. doi:10.1016/j.mayocp.2020.03.015. PMID: 32370842.

Krasimira Rozenova, M.D., Ph.D.
Resident, Anatomic and Clinical Pathology
Mayo Clinic

Diva Salomao, M.D.
Consultant, Anatomic and Clinical Pathology
Mayo Clinic
Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science

An 87-year-old woman with a past medical history significant for invasive bladder cancer was found to have an enlarging mixed solid and cystic lesion in the body/tail of her pancreas on surveillance imaging. She underwent a EUS biopsy and subsequent distal pancreatectomy. The 5.5 cm mass showed the following histology and immunohistochemical profile.

Image: Histology and immunohistochemical profile

This subtype of acinar carcinoma typically harbors alterations in which gene?

  • TP53
  • KRAS
  • MYC
  • RB1

The correct answer is ...


The neoplastic cells coexpress trypsin and neuroendocrine markers without morphologically distinct acinar or neuroendocrine carcinoma components. This neoplasm is best classified as a mixed acinar and neuroendocrine carcinoma (amphicrine type) and is considered a subtype of acinar carcinoma due to shared clinical behavior and genomic features. MYC alterations are present in approximately 55% of pure acinar carcinomas but have been identified in all mixed acinar-neuroendocrine carcinomas investigated. While not associated with a prognostic difference, MYC alterations may play a role in acinar-neuroendocrine differentiation.

TP53, RB1, and KRAS alterations are associated with pancreatic neuroendocrine carcinomas.


  1. Acinar cell carcinoma. In: WHO Classification of Tumours of the Digestive System. 5th ed. IARC Press. 333-335, 2019.
  2. La Rosa S, et al. c-MYC amplification and c-myc protein expression in pancreatic acinar cell carcinomas. New insights into the molecular signature of these rare cancers. Virchows Arch. 2018 Oct;473(4):435-441.
  3. Pancreatic neuroendocrine neoplasms. In: WHO Classification of Tumours of the Digestive System. 5th ed. IARC Press. 343-346, 2019.

Holly Berg, D.O., MLS(ASCP)
Resident, Anatomic and Clinical Pathology
Mayo Clinic

Saba Yasir, M.B.B.S.
Consultant, Anatomic Pathology
Mayo Clinic
Assistant Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science

Mr. and Mrs. Smith were evaluated in the genetics clinic due to a history of multiple miscarriages. Chromosome analysis was ordered for both individuals and demonstrated that Mrs. Smith has a chromosomal abnormality (see a representative karyotype below).

Figure 1: karyotype

Which of the following best represents this couple’s risk of having a liveborn offspring with trisomy 21?

  • 100%
  • 50%
  • 1%
  • 15%

The correct answer is ...


The chromosomal abnormality identified in this patient is an example of a Robertsonian translocation. Robertsonian translocations are the most common type of structural chromosomal abnormality seen in the general population, with an estimated prevalence of 1 per 800-1,000 individuals. This type of translocation results from fusion of the long arms of two acrocentric chromosomes (13, 14, 15, 21, 22). The 13;14 and 14;21 translocations are the most common and account for approximately 85% of all Robertsonian translocations.

The carriers of balanced Robertsonian translocations are phenotypically normal. However, they commonly present with fertility problems, recurrent miscarriages, or children with congenital abnormalities due to an unbalanced form of the translocation, or, in the case of Robertsonian translocation involving imprinted chromosomes (14 and 14), uniparental disomy.

The presence of a chromosomal translocation is often associated with partial or complete spermatogenic arrest, and therefore some male translocation carriers have reduced fertility. In contrast, oogenesis is more likely to progress without an arrest in meiosis despite the presence of a chromosomal translocation. Therefore, the overall risk of having an unbalanced offspring is higher in female carriers compared to male carriers.

The risk of having a liveborn with trisomy 21 in female carriers of the 14;21 Robertsonian translocation is estimated to be 10%-15%, whereas the risk in male carriers is estimated to be 0%-2%.


  1. Gardner & Sutherland, Chromosome Abnormalities and Genetic Counseling, 5th ed., New York: Oxford University Press, 2018
  2. Gersen and Keagle, The Principles of Clinical Cytogenetics, 3rd ed., Springer, New York, NY, 2013
  3. Poot M, Hochstenbach R. Prevalence and phenotypic impact of Robertsonian translocations. Mol Syndromol. 2021 Mar;12(1):1-11. doi:10.1159/000512676. Epub 2021 Feb 17. PMID: 33776621; PMCID: PMC7983559
  4. Hunt PA, Hassold TJ. Sex matters in meiosis. Science. 2002 Jun 21;296(5576):2181-3. doi: 10.1126/science.1071907. PMID: 12077403

Katarzyna Thompson, Ph.D.
Fellow, Laboratory Genetics and Genomics
Mayo Clinic

Nicole Hoppman, Ph.D.
Consultant, Laboratory Genetics and Genomics
Mayo Clinic
Associate Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science

A 43-year-old man presented with intermittent abdominal pain and fevers over the past two years. There was no history of weight loss or jaundice. His MRI showed a suspicious gallbladder fundus mass with potential extension into the liver and accompanying left hepatic atrophy. Cholecystectomy and liver 4B and 5 segmentectomy were performed.

Figure 1
Figure 2

What is your diagnosis?

  • Primary sclerosing cholangitis
  • IgG4 sclerosing cholangitis
  • Segmental cholangiectasia/recurrent pyogenic cholangitis
  • Cholangiocarcinoma

The correct answer is ...

Segmental cholangiectasia/recurrent pyogenic cholangitis.

The patient is a 43-year-old man with intermittent abdominal pain and fevers over the past two years. His MRI showed a gallbladder fundus mass with accompanying left hepatic atrophy, clinically suspicious for a cholangiocarcinoma. Cholecystectomy and liver 4B and 5 segmentectomy were performed. The liver appeared non-cirrhotic. An intraoperative cholangiogram showed common bile duct and intrahepatic duct with a serrated appearance.

The gross pathologic examination of the gallbladder showed hemorrhagic sludgy material. The fundus wall was thickened but there was no mass lesion. The hilum of the liver showed dilated, large intrahepatic bile ducts with wall thickening and increased hilar soft tissue fibrosis.  Intrahepatic calculi were identified. There was also adjacent liver parenchymal atrophy. No mass lesion was identified.

Microscopically, there was bile duct dilation, periductal edema and/or fibrosis, and inflammatory infiltration including neutrophils, lymphocytes, and plasma cells. Bile duct epithelium exhibited patchy regenerative hyperplasia without dysplasia. Focally, prominent periductal lymphoid follicles were noted (Figure 1). Foci of intraductal calculi were also identified (Figure2). There is adjacent liver parenchymal atrophy without cirrhosis. There is no significant ductular reaction.  Gallbladder shows chronic inflammation and prominent reactive lymphoid follicles, consistent with follicular cholecystitis. Immunostains of IgG4 and IgG were performed on one perihilar section and highlighted positive plasma cells without an IgG4 predominance. IgG4/IgG ratio is less than 5%.

This is a case of severe chronic cholangitis. The presence of intrahepatic bile duct ectasia with hepatolithiasis, predominantly affecting left lateral segment and parenchymal atrophy, fits the description of segmental cholangiectasia (i.e., recurrent pyogenic cholangitis ) of the liver.

Segmental cholangiectasia is a recently described rare entity (reference 1) in non-Asian population. Since it shares similar histologic features with classic recurrent pyogenic cholangitis, which is more common in Asian population (reference 2 and 3), the two entities are currently considered as the same diagnostic category. The etiology and pathogenesis of the disease is still speculative. However, recently, a hypothesis centered on the role of E. coli in promoting bile precipitation through its bacterial β-glucuronidase activity has gained popularity. Chronic bacterial infection of the intrahepatic bile ducts can induce inflammation and scarring, eventually leading to stenosis, proximal cholangiectasia, and hepatolithiasis. There appears a propensity to involve the left lateral segment, perhaps due to the sharp angulation of intrahepatic bile ducts from the site causing poor drainage.

To differentiate segmental cholangiectasia/recurrent pyogenic cholangitis from primary sclerosing cholangitis (PSC) can be challenging. Although most PSC involves entire biliary tree without a left segmental propensity, intrahepatic segmental PSC has been reported.  Nonetheless, PSC tends to occur in relatively young patients, often associated with a clinical history of inflammatory bowel disease. Histologically, PSC often presents with fibro-obliterative lesion, ductal loss, marked ductular reaction, chronic cholestasis and eventually biliary cirrhosis.  These are not common findings in cases of segmental cholangiectasia/recurrent pyogenic cholangitis. In fact, lack of exuberant ductular reaction in the adjacent liver parenchyma appears a useful feature to distinguish the two diseases.

Localized Caroli disease is rare but may be confused with segmental cholangiectasia/recurrent pyogenic cholangitis. However, it is a hereditary condition often discovered in young age with renal abnormalities. A family history of cystic kidney disease is a helpful distinction.

There are also many benign conditions presenting as bile duct ectasia with periductal fibrosis, such as ischemic cholangiopathy, IgG4 sclerosing cholangitis, Langerhans cell histiocytosis, etc. In general, their respective characteristic clinical and histologic features are distinct enough not to be confused with segmental cholangiectasia/recurrent pyogenic cholangitis. For example, IgG4 positive plasma cells are significantly increased in IgG4 sclerosing cholangitis while they are rare in segmental cholangiectasia/recurrent pyogenic cholangitis.

Lastly, the clinical presentation and radiographic findings of segmental cholangiectasia/recurrent pyogenic cholangitis are usually alarming for cholangiocarcinoma or intraductal neoplastic process. A careful gross and histologic examination of the resection specimens is always warranted to exclude such possibilities.


  1. Zhao L, Hosseini M, Wilcox R, Liu Q, Crook T, Taxy JB, Ferrell L, Hart J. Segmental cholangiectasia clinically worrisome for cholangiocarcinoma: comparison with recurrent pyogenic cholangitis. Hum Pathol. 2015 Mar;46(3):426-33. doi: 10.1016/j.humpath.2014.11.019. Epub 2014 Dec 9. PMID: 25600951.
  2. Tsui WMS, Lam PWY, Lee W-K, Chan Y-K. Primary hepatolithiasis, recurrent pyogenic cholangitis, and oriental cholangiohepatitis: a tale of 3 countries. Adv Anat Pathol 2011; 18:318-28.
  3. Tsui WMS, Chan Y-K, Wong C-T, Lo Y-F, Yeung Y-W, Lee Y-W. Hepatolithiasis and the syndrome of recurrent pyogenic cholangitis: clinical, radiologic, and pathologic features. Semin Liver Dis 2011; 31:33-48.

Recep Nigdelioglu, M.D.
Fellow, Surgical Pathology
Mayo Clinic

Eric Chen, M.D., Ph.D.
Consultant, Anatomic Pathology
Mayo Clinic
Associate Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science

A 55-year-old man presented with balance and coordination issues, and imaging showed a heterogeneously enhancing mass involving the right thalamus. Biopsy showed a hypercellular infiltrating glioma with atypia and mitotic activity, but no microvascular proliferation or tumor necrosis. By immunohistochemistry, tumor cells were positive for Olig2, negative for IDH1-R132H and H3K27M, and showed retained expression of ATRX. By sequencing and chromosomal microarray, TERT promoter mutation, gain of chromosome 7, monosomy 10, and homozygous deletion of CDKN2A/B on 9p21.3 were identified.

Figure 1: T1-weighted pre- (a) and post-contrast (b) MRI
Figure 2: (a) H&E, (b) Olig2, (c) IDH1-R132H, (d) H3K27M
Figure 3:  Chromosomal microarray analysis

Which of the following molecular features of this IDH-wildtype diffuse astrocytic glioma qualifies it for a diagnosis of “glioblastoma, IDH-wildtype (CNS WHO grade 4)” even in the absence of classic histologic high-grade features?

  • Codeletion of chromosomes 1p and 19q
  • Combined gain of chromosome 7 and loss of chromosome 10
  • MGMT promoter methylation
  • CDKN2A homozygous deletion

The correct answer is ...

Combined gain of chromosome 7 and loss of chromosome 10.

The diagnosis in this case is “Glioblastoma, IDH-wildtype (CNS WHO Grade 4)” according to the recently released 2021 World Health Organization Classification of Tumours of the Central Nervous System. Consistent with the previous classification, infiltrating gliomas without an IDH1 or IDH2 mutation are classified as WHO grade 4 if tumor necrosis or microvascular proliferation are identified histologically. However, in the updated 2021 classification, three molecular features associated with poor prognosis may qualify IDH-wildtype infiltrating gliomas as glioblastoma even in the absence of these high-grade histologic features: 1) EGFR amplification, 2) combined gain of chromosome 7 and loss of chromosome 10, and 3) TERT promoter mutation.1 Thus, this case meets the integrated histologic and molecular features of “Glioblastoma, IDH-wildtype” given that it is an infiltrating glioma with both a TERT promoter mutation and combined copy number gain of chromosome 7 and loss of chromosome 10.

Of note, H3 K27 alterations must be excluded in IDH-wildtype infiltrating gliomas involving the midline, and tumors with these molecular alterations are best classified “Diffuse midline glioma, H3 K27-altered.” In this case, such alterations were not detected by immunohistochemistry or sequencing analysis.

Homozygous deletion of CDKN2A and/or CDKN2B on chromosome 9p is detected in a variety of tumors of the central nervous system, and has increased significance in the 2021 CNS WHO classification. Similar to IDH-wildtype infiltrating astrocytomas, IDH-mutant infiltrating astrocytomas may also reach a grade 4 designation by either histologic criteria (tumor necrosis and microvascular proliferation) or molecular criteria. Specifically, the presence of homozygous deletion of 9p including CDKN2A and/or CDKN2B are sufficient to categorize an IDH-mutant infiltrating astrocytoma as “Astrocytoma, IDH-mutant (CNS WHO grade 4)” even in the absence of classic high-grade histologic features.1

MGMT promoter methylation is frequently detected in high-grade infiltrating gliomas, both IDH-mutant and IDH-wildtype, and is associated with a more favorable response to alkylating chemotherapy, such as temozolomide compared with non-methylated tumors.2 While MGMT promoter methylation is common and predictive of treatment response in glioblastoma, IDH-wildtype, it is neither specific, nor required for the diagnosis. Finally, codeletion of chromosome arms 1p and 19q is characteristic of oligodendrogliomas, and is now required for the diagnosis, the terminology of which has been updated to “Oligodendroglioma, IDH-mutant and 1p/19q-codeleted” in the 2021 WHO classification.1


  1. WHO Classification of Tumours Editorial Board. Central nervous system tumours [Internet]. Lyon (France): International Agency for Research on Cancer; 2021 [cited 2022 Jan 25]. (WHO classification of tumours series, 5th ed.; vol. 6). Available from:
  2. Hegi ME, Diserens AC, Gorlia T, Hamou MF, de Tribolet N, Weller M, Kros JM, Hainfellner JA, Mason W, Mariani L, Bromberg JE, Hau P, Mirimanoff RO, Cairncross JG, Janzer RC, Stupp R. MGMT gene silencing and benefit from temozolomide in glioblastoma. N Engl J Med. 2005 Mar 10;352(10):997-1003. doi:10.1056/NEJMoa043331. PMID: 15758010.

Garrett Fitzpatrick, M.D.
Fellow, Neuropathology
Mayo Clinic

Jorge Trejo-Lopez,  M.D.
Senior Associate Consultant, Anatomic Pathology
Mayo Clinic
Assistant Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science

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