MEETING No. 19, HELD ON APRIL 12th AT THE MELLONI HOSPITAL, MILAN

Case 1 Case 2
Case 3

"MEDIASTINAL MASS"
M. LUCIONI - Policlinico San Matteo - Pavia
(pict. by dr. Lucioni)

Clinical history: a 15y.o. boy in December 1999 is admitted to another hospital for worsening mediastinal syndrome with a six months history of cough, asthenia and feveret.
He is treated with steroids with moderate results and undergoes a biopsy of the mediastinal mass (pict. 1).
Sections of this biopsy show vascularized fibrous connective tissue with some inflammatory cells. Diagnostic hypothesis on this biopsy were: mesenchymal lesion, inflammatory pseudo-tumor or sclerosing mediastinitis.
In February 2000 he is admitted to the Pediatric Clinic I.R.C.C.S. San Matteo, Pavia. Hematological investigations show increased levels of ESR, LDH and ferritin; a Ct scan shows multiple, nodular lesions bilaterally in the kidneys.
A renal biopsy with frozen section examination is performed which shows a proliferation of medium and large cells with a high mitotic index; a diagnosis of malignant poorly differentiated tumor (“blue cells tumor”) is made and the differential diagnosis includes Lymphoma (Hodgkin, mediastinal B cell, lymphoblastic), leukemia, blastematous nephroblastoma, neuroblastoma, Ewing sarcoma/PNET, rhabdomyosarcoma.
Microscopic description: a diffuse proliferation of medium and large sized cells with high N/C ratio (pict. 2) - (pict. 3) - (pict. 4) is present.
The convoluted nuclei have fine chromatin and small nucleoli. There are numerous mitosis; eosinophils are rare.
Immunohistochemical staining with antisera for Cytokeratin, Desmin, Actin, MPO, lysozime, NSE, Chromogranin A, CD1, CD4, CD8, CD20, CD79a are all negative; Vimentin and CD45 are weakly positive; staining with antisera for CD10/CALLA (pict. 5), CD3 (pict. 6), TdT (pict. 7), CD99 (pict. 8) and CD43 are strongly positive.

Diagnosis

pict. 1	pict. 2
pict. 3	pict. 4
pict. 5	pict. 6
pict. 7	pict. 8

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