Diffuse Strong Membrane Expression of MIC2 (CD99) in Anaplastic Large Cell Lymphoma: A Diagnostic Challenge

The MIC2 [Cluster of Differentiation 99 (CD99)] has been widely used in making the diagnosis of Ewing’s sarcoma and diffuse strong membrane expression is the characteristic finding. The CD99 is a sensitive marker of Ewing’s sarcoma, but not specific. Studies have shown expression of CD99 in a wide variety of neoplasms which include epithelial, mesenchymal and haematopoietic neoplasms. In these tumours, the positivity of CD99 is described as variable with focal/patchy, irregular, membrane/cytoplasmic staining. Among the haematopoetic neoplasms, diffuse strong positivity of CD99 is seen in blasts which include T-lymphoblasts, B-lymphoblasts and myeloblasts. Recent studies have demonstrated positive staining of CD99 in mature lymphomas where the pattern of expression is heterogenous and highly variable. Herein, authors report the case of a 42-year-old male patient with expansile destructive lesion in right scapula with large soft tissue component. With clinical diagnosis of sarcoma, biopsy was taken which showed large atypical cells arranged diffusely, focally around vessels and in vague rosettoid pattern. In the initial immunopanel, neoplastic cells showed diffuse strong membrane expression of CD99 and were negative for cytokeratin, synaptophysin, chromogranin, desmin and S100. On further examination, the neoplastic cells showed focal weak to moderate positivity for CD45, diffuse strong positivity for CD30 and strong positivity for Anaplastic Lymphoma Kinase (ALK). Diagnosis of ALK positive Anaplastic Large Cell Lymphoma (ALCL) was given. The awareness of diffuse strong membrane pattern of staining of CD99 in ALCL will help to avoid misdiagnosis especially in cases with atypical clinical presentations.

Composite lymphomas: Experience from a tertiary cancer center in Kerala, South India

OBJECTIVES

Composite tumors are defined as tumors in which there are two different intermixed histologic types. Our objective was to study the clinical and pathologic features of five cases of composite lymphoma.

MATERIALS AND METHODS

Our study included five patients of composite lymphoma diagnosed over a period of 5 years. Clinical presentation, hematological parameters including peripheral smear, bone marrow aspirate, and histopathological examination of lymph node including immunohistochemistry (IHC) were studied. Treatment and follow-up details were also noted.

RESULTS

All the five cases were in the adult age group ranging from 44 to 72 years. All the cases were composite follicular lymphoma (FL) and mixed cellularity classical Hodgkin lymphoma (CHL). Diagnosis in all cases was suspected on morphology by identification of distinct neoplastic follicles in FL and classic Reed-Sternberg cells in CHL and confirmed by IHC.

CONCLUSION

Although rare, composite lymphomas should be kept in mind. Careful histopathological examination of lymph node with identification of distinct morphological features along with IHC helps to arrive at the definitive diagnosis.

Wolman Disease: A Mimic of Infant Leukemia

BACKGROUND

Infant leukemia most commonly present with pallor and hepatosplenomegaly. The possibility of other differential diagnosis also has to be kept in mind during evaluation, as identifying the precise etiology for this clinical presentation is crucial for management.

OBSERVATION

An infant, was referred to us with suspected infant leukemia and was subsequently diagnosed to have lysosomal acid lipase deficiency/Wolman disease with a novel 5 bp deletion "c.1180_1184del" in the last exon (exon 10) of the lipase A (LIPA) gene.

CONCLUSIONS

Hepatosplenomegaly and pallor resulting from nutritional deficiency or bone marrow involvement in Wolman disease can mimic infant leukemia.

Malignant melanoma of breast: a unique case with diagnostic dilemmas

Melanomas arising in the skin, mucous membranes, and eye are encountered commonly than melanomas involving the breast. Melanomas in the breast are usually metastatic. Primary melanoma of the breast is extremely rare. We report a case of malignant melanoma of breast (primary/metastatic) that presented as a breast lump in a patient with no detectable cutaneous, mucosal or ocular lesion and who is a known case of squamous cell carcinoma of the oral cavity and had relapsed twice. The unexpected challenges faced during the diagnosis prompted us to report this case.