Abstract

Introduction:

Pericytoma with t(7;12) is a unique and exceedingly rare type of myopericytic neoplasm, with few cases reported in the literature.  Although cases involving the tongue have been described, the current case represents the first pericytoma with t (7;12) to arise in the hard palate.

Case history:

The patient was a 63-year-old man, with a three-month history of a left hard palate mass.  A CT scan showed a 3.0 x 2.6 x 2.4 cm left hard palate mass projecting into the left maxillary sinus.

Histology and Molecular:

Histopathologic evaluation of the specimen demonstrated a cellular neoplasm composed of vesicular cells with vacuolated cytoplasm and central nucleoli admixed with prominent vasculature and extravasated red blood cells. The tumor was predominantly solid, focally ulcerated, and extended to the margins of the excision.

The neoplastic cells were focally immunoreactive for smooth muscle actin. Weak positivity for pan-TRK was noted. In contrast, the neoplastic cells failed to stain with antibodies to cytokeratin AE1/AE3, CD1a, desmin, S-100 protein, chromogranin, HMB45, TFE3, p60, p43, HHV-8, and STAT6. Cells lining the vessels were stained with CD34 and ERG.  A preliminary diagnosis of “Epithelioid and spindled mesenchymal neoplasm of uncertain malignant potential” was issued and the blocks were sent for a sarcoma comprehensive NGS fusion panel. An ACTB:GL1 fusion transcript [t(7;12)(p22.1;q13.3)]  was detected.

This unique case is histologically challenging as it does not have a definite immunophenotypic profile and poses a diagnostic dilemma. Molecular studies, including NGS, can be very helpful in the characterization of such tumors.