CM-05. Surgical management of a histiocytic tumor of unknown malignancy potential: Case report
Vsevolod G. Potapenko1, Yurij A. Krivolapov2, Elena E. Leenman2, Jean-François Emile3
1 Municipal Clinical Hospital No.31, St. Petersburg, Russia
2 North-Western State I. I. Mechnikov Medical University, St. Petersburg, Russia
3 Hôspital Ambroise Paré, Paris, France
Dr. Vsevolod G. Potapenko, e-mail: firstname.lastname@example.org
Approach to histiocytic tumors management depends on extent of the disease. One of possible approached consists of surgical resection of a single lesion. We present a case report of a patient with axillary histiocytic tumor of unknown malignant potential.
A 64 y.o. woman complained of axillary lymph node enlargement starting in January 2019. The ultrasound scan showed an enlarged lymph node (4.6×2.3×2 cm). In July 2019 it was completely excised. The microscopic examination showed diffuse proliferation of large cells with small nuclei, barely visible nucleoli, ample eosinophilic cytoplasm. Some cells contained small, optically empty vacuoles. There were 7 to 10 mitotic figures per HPF, some clusters of xantomous cells. The infiltrate also contained diffuse small lymphocytes with hyperchromic round nuclei and plasma cells. Some residual lymphoid tissue retained lymphoid follicle architecture, without germinal centers (Fig. 1). The tumor stroma was diffusely fibrotic. Most atypical cells expressed CD45, CD68, MNDA, FXIII, cyclin D1 (except xanthomatous cells). Single cells expressed CD1a. Xanthomatous cells showed intensive adipophilin expression. Within the residual lymphoid follicles there were prevalent cells with CD20, MNDA expression negative for CD5, CD23, cyclin D1, LEF-1. Immunoglobulin light chain expression was polytypic. Most infiltrating lymphoid cells were diffusely located and represented by CD3/CD5-positive T-cells. There were no pancytokeratin, CK7 or CK20-expressing cells in the sample. Ki-67 was 20–25 % in hotspots. Based on the morphological characteristics and the immunoprofile the tumor was signed as a histiocytic tumor of unknown malignant potential. NGS revealed a probable pathogenic sequence: BRAF c.[1337C>T; 1340 G>A] (variant allele frequency 1.8%), and CBL c.1256G>A, (variant allele frequency 16 %). Whole body PET-CT scan performed at 3 months after resection revealed no metabolically active lesions. Currently there is no evidence of disease progression (25 months follow up).
Radical surgical resection of the histiocytic tumor of unknown malignant potential led to a long lasting curative result.
Histiocytosis, unknown malignancy potential, BRAF.
Figure 1. Morphology of the histiocytic tumor: Azur and eosin stain, x400 (A) ; expression of CD68 by the atypic cells in the infiltrate, x200 (B)