| Abstract|| |
Granular cell tumors (GCT) are uncommon tumors of uncertain histogenesis. They may occur at any site and most commonly involve the tongue, breast, upper respiratory tract, and soft tissue of upper extremities; however, the involvement of skin is rare. The cytological findings of cutaneous GCT are limited to a few cases being reported till date; we report a case of cutaneous granular cell tumor in a 42-year-old male.
Keywords: Cutaneous; cytology; granular cell tumor
|How to cite this article:|
Goel G, Singh N, Gupta R, Jain S. Recurrent benign cutaneous granular cell tumor: A case report. J Cytol 2013;30:287-8
| Introduction|| |
Granular cell tumors (GCT) were initially thought to be of myogenic origin; however, based on the electron microscopic and immunohistochemical evidence, a neural origin has been proposed. These tumors may occur at any site, most frequently involving the tongue, and can be benign or malignant.  In the past, cytological features of GCT have been reported predominantly on bronchial washings and brushings and in fine needle aspiration cytology (FNAC) of breast.  Skin is rarely involved by GCT and hence cytology of GCT have been infrequently reported in the past. We present here the cytological features of cutaneous GCT in a 42-year-old male.
| Case Report|| |
A 42-year-old male presented to surgery OPD with a gradually increasing, painful, right-sided swelling in the back for two years. There was no history of any other painful nodules or local trauma. On physical examination, a firm, mobile subcutaneous swelling with well-defined margins, measuring 7 × 6 cm in size was noticed over right side of back. No discoloration or vascular distension was identified [Figure 1]a. Past history of excision of similar swelling from the same site few years back was present; however, records of previous surgery were not available.
|Figure 1: (a) Well circumscribed soft tissue swelling on the back (b) FNA smears showing few multinucleate cells (Giemsa, ×400) along with few cells with intranuclear inclusions (Inset) (Giemsa, ×600) (c) Section from cell block showing uniform granular cells with low N: C ratio (H and E, 400) S100 positive tumor cells (IHC, ×400) (d) Section from cell block showing cells with PAS-positive, diastase-resistant granular cytoplasm (PAS with diastase, ×400)|
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A FNA of the swelling was performed using standard technique. The smears prepared from the aspirate were air dried and stained with Giemsa stain. A portion of the aspirate was submitted for cell block. Sections from the cell block were stained with hematoxylin and eosin (H and E). The FNA smears revealed moderate to high cellularity comprising of singly scattered as well as clusters of uniform polygonal cells with low N/C ratio, moderate to abundant granular, fragile cytoplasm, and eccentrically placed round to oval nuclei with few cells showing mild nuclear pleomorphism [Figure 1]b. A small number of cells had prominent nucleoli while occasional cells showed prominent intranuclear inclusions [Figure 1]c. Few binucleate and multinucleate cells were also noticed. No necrosis or mitoses was identified. Based on the cytomorphological features, a diagnosis of granular cell tumor was given. The cell block sections showed uniform polygonal cells with periodic acid- Schiff (PAS)-positive, diastase-resistant granular cytoplasm The cells also demonstrated positivity for S100 [Figure 1]d. Hence, the diagnosis of granular cell tumor was confirmed.
| Discussion|| |
GCT is a multifocal tumor usually presenting in the fourth to sixth decades of life with a slight preponderance in adult females.  In majority of the cases, distinctive cytological features aid in an easy diagnosis of GCT on FNAC. ,, However, discrimination from lesions like malignant GCT, alveolar soft part sarcoma, rhabdomyoma, histiocytes, and fat necrosis is essential. ,
Cytological features in the present case were comparable to those described in the earlier reports. The multinucleate cells seen in the present case were similar to the giant cells described by Thomas et al.  The previously unreported nuclear pleomorphism described by Liu et al. in all the three cases of benign GCT was noticed in our case. The presence of prominent intranuclear cytoplasmic inclusions in few cells first illustrated by Liu et al. is a significant cytomorphologic feature and was prominently observed in the present case. This finding has been observed in many other neoplasms like malignant melanoma, bronchioloalveolar carcinomas, and thyroid carcinomas. 
Malignant GCT accounts for 1 to 2% of all cases of GCT. In contrast to benign GCT which usually measures <3 cm, malignant GCT are usually >5 cm in diameter. Histologically, malignant GCT can be differentiated from benign GCT by presence of increased cellularity, necrosis. and mitosis (>2/10 high power fields at ×200 magnification). ,,, In the present case, size of the tumor was 7 cm, still it was labeled as benign due to the absence of both necrosis and mitosis.
The present case was that of a recurrent GCT. Benign granular cell tumors have a recurrence rate of 2 to 8% when resection margins are deemed clear of tumor infiltration and is increased to 20% when the resection margins of a benign granular cell tumor are positive for tumor infiltration. 
The primary lesion which needs to be discriminated from GCT is alveolar soft part sarcoma, which shows cells with prominent nucleoli, multinucleate giant cells, thin-walled vasculature, and rhomboid crystals.  The presence of cross striations and use of special stains to show skeletal muscle differentiation may help distinguish rhabdomyoma from GCT.  S-100 positivity in GCT helps exclude alveolar soft part sarcoma and rhabdomyoma. 
The granular cells of GCT may resemble histiocytes, but the discrete nuclear features help identify the two correctly. Histiocytes have a bean-shaped to oval nucleus in contrast to the round nucleus of granular cells. Also, the cytoplasm of histiocytes is more foamy than granular. , Cytology of fat necrosis shows multinucleate cells along with cells having a foamy instead of granular cytoplasm. 
| Conclusion|| |
To conclude, GCT rarely presents as a cutaneous lesion and has a characteristic cytological appearance, permitting an easy diagnosis. Though literature describes malignant GCTs to be much larger than benign ones, this case report describes a benign GCT which was large and recurrent. Presence of nuclear pleomorphism and few multinucleate cells should not lead to a false impression of malignancy. Presence of intranuclear inclusions should be added as a useful identification feature.
| References|| |
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Department of Pathology, Maulana Azad Medical College, New Delhi - 110 002
Source of Support: None, Conflict of Interest: None