Ectopic micronodular thymoma with lymphoid stroma

Autor: Susanne Mende, Alexander Marx, R. Hubert Laeng, Michael Moschopulos
Rok vydání: 2004
Předmět:
Zdroj: Virchows Archiv. 444:397-399
ISSN: 1432-2307
0945-6317
Popis: Sir, Micronodular thymoma (MNT) with lymphoid B-cell hyperplasia, a recently described rare benign neoplasm of thymic epithelium, has been found, thus far, invariably in the anterior mediastinum. We present herein an ectopic MNT incidentally found in the left cervical region related to the parotid gland. Another novel finding is partial myoid differentiation of neoplastic epithelial cells. A 45-year-old otherwise healthy man appeared in consultation for a feeling of hearing loss when a left cervical tumour was incidentally found. There was neither myasthenia gravis nor any other autoimmune diseases. The tumour, clinically suspicious for cervical lymphadenopathy, was encapsulated and could be completely removed, although minimally adherent with the parotid gland. A follow-up control 1 year after surgery found the patient free of recurrence. At gross examination, the tumour measured 3.5 cm, exhibited a microcystic cut surface and was completely enclosed in a thin fibrous capsule. Histologically, solid micronodules of neoplastic epithelial cells stood out against a lymphoid stromal background in close relationship with the parotid gland (Fig. 1); normal ectopic thymus was not observed. Periodic acid-Schiff and reticulin stains highlighted a delicate envelope of epithelial complexes, but reticulin fibres did not surround individual cells. Using immunohistochemistry, the neoplastic epithelial cells were reactive for cytokeratins (5, 6, 8, 17) and alpha-smooth muscle actin (a-SMA, Fig. 2), but non-reactive for desmin, myoglobin, myogenin, S-100 protein, glial fibrillary acid protein (GFAP) and CD20. In the stromal compartment, reactive lymph follicles displayed hyperplastic germinal centres (Fig. 1 and Fig. 2) and a polyclonal B-cell population, including a minor fraction of immunohistochemically polytypic plasma cells. Polymerase chain reaction for Ig heavy chain gene rearrangement also indicated the presence of polyclonal B cells. There were considerable numbers of CD3+ mature T cells
Databáze: OpenAIRE
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