Final Diagnosis -- Spindle/sclerosing variant of follicular lymphoma

FINAL DIAGNOSIS

Spindle/sclerosing variant of follicular lymphoma.

After surgery, when examining minutely medical history in detail, the patient reported a history of exposure to schistosome-infected water. Then, the patient was treated with praziquantel (20mg/kg per day) for 6 days with concurrent administration of dexamethasone. The patient was followed up 5 months later with complete resolution of the symptoms, companying with the complete disappearance of lesion on MR images.

DISCUSSION

Spindle cell features in hematopoietic neoplasms are unusual and must be differentiated from true sarcomas. Cases have been reported in the skin, subcutaneous tissue, mediastinum, and nasal mucosa/paranasal sinus (4), and more conventional lymphomas can occur in the dura (3). The current tumor most likely arose in the skull. Such rare cases have been described previously but none have involved the dura.

Radiologically, the differential diagnosis for skull-dural lymphoma is broad and includes high grade meningioma, metastasis, solitary fibrous tumor, leiomyosarcoma, inflammatory pseudotumor, neurosarcoidosis, and Castleman's disease.

Histologically, these spindle cell features do not raise suspicion of a lymphoma, but rather suggest a sarcoma. Metastatic spindle cell neoplasms such as spindle cell carcinoma, spindle cell melanoma, or dendritic cell sarcoma, could also resemble this tumor. Neoplastic lymphocytes are known to assume a spindled morphology when infiltrating into bone and soft tissues (2), but to have an entire tumor show such prominent spindling, without any cytologic hint of lymphoma, is very unusual. Immunohistochemistry is therefore critical to confirm the lymphocytic origin of these tumors. The spindle cell variant of B-cell lymphoma exhibits both phenotypic and genotypic markers of germinal B cells, with mutations of immunoglobulin and BCL-6 and co-expression of CD-10, BCL-6, MUM1, and CD138 (1).

Spindle cell lymphoma is a rare morphological variant of B-cell lymphoma and, to the best of our knowledge, has not previously been described in the dura. This case underscores the importance of keeping a very broad differential in mind, and the importance of using hematopoietic immunohistochemical markers, even when microscopic examination does not suggest such a tumor.

REFERENCES

1. Carbone A, Gloghini A, Libra M, Gasparotto D, Navolanic P, Spina M, et al (2006) A spindle cell variant of diffuse large B-cell lymphoma possesses genotypic and phenotypic markers characteristic of a germinal center B-cell origin. Modern Pathology. 19:299-306.
2. Nozawa Y, Wang J, Weiss LM, Kikuchi S, Hakozaki H, Abe M (2001) Diffuse large B-cell lymphoma with spindle cell features. Histopathology. 38:177-8.
3. Tandon R, Mukherjee U, Abrari A, Patir R, Tandon A, Bansal B (2012) Primary dural follicular lymphoma masquerading as meningioma: a case report. British Journal of Neurosurgery.26:905-906.
4. Wang J, Sun N, Nozawa Y, Arber D, Chu P, Chang K, et al (2001) Histological and immunohistochemical characteristics of extranodal diffuse large-cell lymphomas with prominent spindle cell features. Histopathology. 39:476-481.

Contributed by Melanie H. Hakar, DO, Benjamin P. Liu, MD, Craig M. Horbinski, MD