Case 15

A 70-year-old male with a parotid lesion. Biopsy was done.

1. What's the diagnosis by morphology?

   A: pleomorphic adenoma

   B: Basal cell adenoma

   C: Salivary duct with squamous and mucinous metaplasia

   D: Low grade neoplasm favor benign

   E: Low grade neoplasm favor malignant

   F: Carcinoma, recommend resection

   G: Carcinoma favor adenoid cystic carcinoma

   H: Carcinoma favor mucoepidermoid carcinoma

   
   

Answer

There is no correct answer however, considering and favor any malignancy is more appropriate. Figure A showed the parotid gland which is purely serous gland. The tumor nests are somewhat irregular and the intraluminal vacuoles are positive for mucicarmine. This finding is relatively concerning for MEC.

Several entities can be considered when diagnosing low-grade MEC, including mucocoele, necrotizing sialometaplasia, sclerosing sialadenitis with mucous metaplasia, pleomorphic adenoma.

CRTC1::MAML2 fusion is most reliable and specific findings suggestive for MEC.

-Small fragments suspicious for salivary gland neoplasm.

-See comment.

COMMENT: Some features are suggestive of mucoepidermoid carcinoma; however, the biopsy fragments are minute and may not be representative of the entire lesion.

A case of MEC with predominantly cystic and some focal papillae and mucin

Reference: https://tumourclassification.iarc.who.int/chaptercontent/52/77

Case credit: UCSD Pathology

Author: Wangpan Jackson Shi, MD