Case 123

A 64-year-old female with a left groin enlarged lymph node

1. What's the diagnosis?

   A: Intranodal palisaded myofibroblastoma

   B: MPNST

   C: Angiosarcoma

   D: Schwannoma

   E: Kaposi sarcoma

Answer

The correct answer is A. This is a spindle cell neoplasm in the lymph node.

Lesional cells are positive for beta-catenin and cyclin D1 (bcl-1), are are negative for S100, CD34, myogenin, STAT6, MUC4, desmin, SMA, ER, and PR, consistent with the rendered interpretation. TLE1 shows some staining of unclear significance.

Category

Features

Architecture

Moderately to highly cellular; short fascicles and whorls of spindle cells; fibromatosis-like areas

Stroma

Finely collagenous to myxocollagenous with extravasated erythrocytes and/or hemosiderin

Characteristic Structures

Variably shaped, dense collagenous bodies; vessels with hyalinized walls

Cellular Features

Spindle cells with scant, lightly eosinophilic cytoplasm; perinuclear vacuoles; salmon-coloured cytoplasmic inclusions

Nuclei

Elongated, focally wavy, cytologically bland; mitotic rate: 0–8 mitoses/5 mm²

Immunohistochemistry - Positive

Diffuse: Vimentin, SMA, MSA Variable: Calponin, Podoplanin (D2-40), Factor XIIIa, nuclear β-catenin, Cyclin D1 Focal: Desmin

Immunohistochemistry - Negative

Cytokeratins, S100, CD21, CD23, CD35 (FDC markers), CD31, CD34, von Willebrand factor (vascular markers), KSHV/HHV8

Proliferation Index

Ki-67 < 5%

Differential Diagnosis

Kaposi sarcoma

References: https://tumourclassification.iarc.who.int/chaptercontent/63/334

Case credit: UCSD pathology

Author: Wangpan Jackson Shi, MD