| Abstract|| |
Subcutaneous panniculitic-like T-cell lymphoma constitutes a distinctive clinicopathologic entity derived from cytotoxic T lymphocytes. A 25-year-old female presented with fever and skin lesions over the upper limb, lower limb and trunk since 2 years. On examination, there were multiple subcutaneous, tender, erythematous, poorly circumscribed indurated plaques and nodules on the upper limbs and lower limbs. Histopathological examination revealed subcutaneous fat displaying a predominantly lobular infiltration of atypical lymphoid cells. Characteristically, there was rimming of individual fat cells by the surrounding neoplastic lymphocytes. Immunohistochemical evaluation of the neoplastic lymphocytes showed CD3 and CD5 immunoreactivity and CD30 and CD20 negativity. A diagnosis of subcutaneous panniculitic T-cell lymphoma was made. SPTCL is a rare cytotoxic lymphoma that can be misdiagnosed as benign panniculitis due to similarities in clinical and histological features between the two entities and thus cause a diagnostic hindrance.
Keywords: Lymphoma, panniculitis, subcutaneous
|How to cite this article:|
Vijaya B, Sunila M D, Manjunath G V. Subcutaneous Panniculitic-Like T-Cell Lymphoma: A red alert! The role of a vigilant histopathologist. Indian J Pathol Microbiol 2011;54:376-8
|How to cite this URL:|
Vijaya B, Sunila M D, Manjunath G V. Subcutaneous Panniculitic-Like T-Cell Lymphoma: A red alert! The role of a vigilant histopathologist. Indian J Pathol Microbiol [serial online] 2011 [cited 2020 Nov 30];54:376-8. Available from: https://www.ijpmonline.org/text.asp?2011/54/2/376/81647
| Introduction|| |
Subcutaneous Panniculitic - Like T-Cell Lymphoma (SPTCL) was described in 1991 by Gonzalez and colleagues as a group of lymphomas localized primarily in the subcutaneous tissue. The lesions described were subcutaneous nodules mimicking panniculitis.  SPTCL constitutes a distinctive clinicopathologic entity derived from cytotoxic T lymphocytes. It was first included as a provisional entity in the real classification as subcutaneous panniculitic T-cell lymphoma. It was also accepted as a rare cytotoxic T-cell lymphoma and was included within the group of other extranodal T-cell neoplasms in the World Health Organization (WHO) classification of tumors of hematopoietic and lymphoid tissues. 
| Case Report|| |
A 25-year-old female presented with skin lesions and fever since 2 years. The lesions were present on the upper limbs, lower limbs and trunk. They were not associated with itching. Fever was associated with malaise, fatigue and myalgia.
On examination, there were multiple subcutaneous, tender, erythematous, poorly circumscribed indurated plaques and nodules, ranging from 1cm to 4 cm, on the upper limb and lower limb. There was no ulceration of the nodules. There was no organomegaly or palpable lymph nodes. The patient had pallor. The hematological investigations showed the following: Hb 6.6 g/dl; Total count 3480 cells/mm 3 ; differential count was in the normal range and erythrocyte sedimentation rate (ESR) was 30 mm at the end of 1 hour; HIV status non reactive.
Patient had these complaints for the past 2 years. She was investigated and treated elsewhere before she came to the present hospital. Serological investigations for systemic lupus erythematosus (SLE) were negative. Biopsy done from one of the lesions in right forearm elsewhere was reported as chronic form of erythema nodosum without vasculitis. The hematological investigations at that time showed the following: Hb 6 g/dl; total count 3600 cells/mm 3 ; differential count: lymphocytes-46%, neutrophils-51%, basophils-0%, eosinophils-2%, monocytes-1%; ESR 35 mm at the end of 1 hour.
A repeat biopsy was done from the lesion in the lower limb and subjected to histopathological examination. Grossly, the biopsy consisted of gray-white tissue fragments measuring 0.8 cm in diameter. No skin was included in the biopsy sample. Histopathological examination revealed subcutaneous fat displaying a predominantly lobular infiltration of atypical lymphoid cells [Figure 1]. The interstitium of fat lobules was replaced by pleomorphic small-medium and medium-large atypical lymphocytes with irregular nuclei having dense chromatin. Characteristically, there was rimming of individual fat cells by surrounding neoplastic lymphocytes [Figure 2]. Mitotic figures and karyorrhectic debris were noted. Histiocytes were seen amidst these lymphocytes. However, no erythrophagocytosis was seen and no granuloma was observed.
|Figure 1: Photomicrograph showing subcutaneous fat displaying a predominantly lobular infiltration of atypical lymphoid cells (H and E, ×200)|
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|Figure 2: Photomicrograph showing rimming of individual fat cells by surrounding atypical lymphoid cells (H and E, ×400)|
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Immunohistochemical study showed CD3 and CD5 immunoreactivity and CD30 and CD20 negativity of the lymphoid cells [Figure 3] and [Figure 4]. T-cell receptor gene rearrangement could not be done in this case. A diagnosis of SPTCL was made and the patient was referred to oncology center. Bone marrow aspiration and biopsy did not reveal lymphomatous infiltrate.
|Figure 3: Photomicrograph showing CD3 positive lymphoid cells (3,3'-Diaminobenzidine DAB , ×200)|
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|Figure 4: Photomicrograph showing CD5 positive lymphoid cells (DAB, ×200)|
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| Discussion|| |
SPTCL is most common in young adults and has a female preponderance.  Clinically, patients present with fever and multiple subcutaneous nodules most commonly on the extremities and trunk. Laboratory abnormalities may not be severe even though more than 50% may show cytopenias.  The present case showed leucopenia on two occasions. Metastatic disease or visceral involvement is uncommonly observed in SPTCL.
Histopathologically, there is dense infiltration of subcutaneous fat tissue by small to medium and medium to large sized lymphocytes, predominantly in lobular pattern. Dermal invasion is absent or very minimal. The neoplastic lymphocytes show atypical features like hyperchromatic and angulated nuclei. The lymphomatous infiltrate may be admixed with histiocytes, plasma cells and neutrophils, mimicking benign panniculitis. Characteristic feature of rimming of individual fat spaces by neoplastic lymphocytes will provide a diagnostic clue to this entity although it can be seen in other primary and secondary cutaneous lymphomas. , Granulomatous reaction and erythrophagocytosis may be seen, both of which were not observed in the present case.  Angioinvasion may also be a feature.  The neoplastic lymphoid cells are of cytotoxic T-cell phenotype, which are CD3+, CD4-, CD8+ and CD56- ,, Intense diffuse positivity for cytotoxic granular proteins such as T-cell intracellular antigen 1 (TIA-1) and perforin and granzyme is observed in the tumor cells. , Staining for apoptosis shows numerous positive apoptotic bodies, suggesting apoptosis as the mechanism of cell death in these tumors.  Tumor cells express T-cell receptors. Recent studies suggest that distinction should be made between SPTCL with an αβ T-cell phenotype and γδ T-cell phenotype as they differ in clinical course.  Lymphomas with T Cell Receptor TCR αβ phenotype are usually CD4, CD8+, and CD56 and have an indolent course. On the contrary, lymphomas with γδ phenotype are usually CD4-, CD8- and CD56+ and have an aggressive course. ,,
SPTCL can be misdiagnosed as benign panniculitis clinically and histologically, leading to a delay in definitive diagnosis as occurred in the present case. The subcutaneous lesions resolve spontaneously and respond to systemic steroids in the initial phase of the disease. Hence, it may be mistaken as benign panniculitis. Histologically, the presence of mixed inflammatory infiltrate of lymphohistiocytic cells may give an impression of a benign process. However, a keen observation may show rimming of fat cells by neoplastic lymphocytes, which clinches the diagnosis and forms an important diagnostic clue. Histologically, unlike SPTCL, lupus erythematoses panniculitis does not show rimming of fat cells by lymphocytes. 
SPTCL should also be differentiated from other malignant lymphoid infiltrates involving the subcutis. In primary cutaneous T-cell lymphoma other than SPTCL, the neoplastic infiltrates involve the dermis, and in some subtypes, even the epidermis.  The present case showed minimal dermal tissue which did not show involvement. Rimming of neoplastic lymphocytes is a common finding in SPTCL, whereas it is rarely seen in other types of cutaneous lymphomas. 
| Conclusion|| |
SPTCL is a rare cytotoxic lymphoma that can be misdiagnosed as benign panniculitis due to similarities in clinical and histological features between the two entities. This may lead to delay in the diagnosis. Characteristic rimming of neoplastic lymphoid cells around individual adipocyte should raise a high index of suspicion of this lesion, which can be confirmed on immunohistochemical stains. Long-term follow-up of these patients is important to observe the course of the disease.
| References|| |
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Department of Pathology, JSS Medical College, Mysore
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]