Diagnosis of Bony Metastasis of Renal Cell Carcioma at a Rare Site on Fine Needle Aspiration Cytology: A Rare Case Report

Fine needle aspiration cytology (FNAC) is cheap, non invasive and time saving procedure in diagnosis and management of patients in developing countries. Metastasis of renal cell carcinoma (RCC) to distant sites and organs at time of presentation is not infrequently encountered in the setting of FNAC for initial diagnosis. Here, we present a case of metastatic RCC to right clavicle initially diagnosed on FNAC and was confirmed on radiological examination of abdomen and histopathological examination.


Introduction
Renal cell carcinoma is generally a tumor of adults (average age at diagnosis: 55-60 years). [1] Approximately one-third of patients with renal cell carcinoma already have distant metastasis at the time they seek medical attention. [2] The most common sites of distant metastasis are lungs and skeleton. The bones most commonly involved are pelvis and femur, but there is also a predilection for the sternum, scapula and small bones of the hands and feet. [3,4] Metastasis can also develop in the adrenal gland, liver, skin, soft tissue, central nervous system, ovary and almost any other site. [5] Renal cell carcinoma is actually notorious for metastasizing to the most unusual places such as nasal cavity, oral cavity, larynx, parotid, thyroid, heart, bladder, testis, prostate and pituitary gland. [6] These metastasis are often solitary, at least at the clinical level. [7] Because of this and the fact that primary tumor is often clinically silent, these metastasis tend to be confused with primary tumors of the organs in which they lodge.

Case Report
A 50 year female, presented to the orthopaedics out patient department of our institution with complaint of swelling and pain in right supraclavicular region since 2 months, along with difficulty in over head abduction [ Figure-1]. On local examination, a swelling measuring 5x6cm in size was present over right clavicle; firm in consistency with local raised temperature. On X-ray examination, an osteolytic lesion was seen involving the lateral half of right clavicle with mild soft tissue bulge query neoplastic, infective, inflammatory . Routine investigations showed increased ESR=65mm/hr, CRP= 1.0 mg/dl. Ultrasonography of right clavicle was done which revealed a heterogenous mass (? neoplastic) with predominant hypo-echoeic echo pattern measuring 6.0x9.7 cm in size with increased vascularity on color doppler. Patient was referred to pathology department for FNAC of the clavicular mass.
On examination a pulsatile swelling measuring 5x5 cm size was present on lateral side of right clavicle. FNAC of the clavicular mass was done and hemorrhagic material was aspirated. Smears were stained with May Grunwald Giemsa (MGG) stain.
On microscopic examination blood mixed smears showed low cell yield with epithelial cells forming clusters, papillaroid structures and papillae with focal fibrovascular core [ Figure-

Discussion
Renal cell carcinoma is a tumor with an unpredictable clinical course and behavior. Metastases have been reported to develop 17 years or more after the primary lesion is removed. [8] Annals of Pathology and Laboratory Medicine, Vol. 4, Issue 3, May-June, 2017    preceded only by breast and lung. Metastasis solely to head and neck region occurs in only 1% patients with primary RCC and usually affect thyroid, nose, paranasal sinuses and oral cavity. [10] 29-57% of patients develop metastasis by the time tumor is diagnosed. Only <1% of patients with bone metastasis manifested clavicular RCC metastasis. Thus clavicular metastasis as the initial presentation of RCC is extremely rare. Bony metastasis from RCC are purely lytic, expansile and highly vascular. [11] Clavicular symptoms may be manifested before the diagnosis of primary tumours, such as RCC. Clavicular fracture may be the first symptom of tumor metastases to bones. Distinguishing pathological fractures from clavicular fractures due to other causes may help diagnose the primary tumors. [ 12] Characteristically, the tumor is slow-growing and encapsulated in its early stages and thus asymptomatic. When a patient with a clinically asymptomatic renal cell carcinoma has signs and symptoms referable to a localized lesion, the final diagnosis depends on histologic and cytologic evaluation of a biopsy specimen. [13] Microscopically it can be confused with other clear cell carcinomas. Hughes et al. have described prominent vascularity to be an important feature of RCC to distinguish it from other clear cell tumors. [11] Fuhrman nuclear grade used in histology can be applied in cytology smears. [14] Cells of RCC contain intra cytoplasmic fat, hence Oil Red O staining of air dried smears can be used to distinguish RCC from other clear cell tumors. [15] While metastasis are associated with poor outcome, solitary bone lesions have increased associated survival when compared to multiple bony lesions or a combination of bone and other organs. [16] Local resection without sacrifice of the vital structures is the treatment of choice depending on the site of presentation. This may provide a chance of cure of the head and neck metastasis and avoid associated morbidity that may occur if the lesion is left untreated. [17]

Conclusion
The case is being presented due to its rare site of metastasis, lytic expansible and highly vascular nature of the lesion which can be misdiagnosed and confused with other clear cell carcinomas. Early diagnosis may increase survival and avoid associated morbidity without sacrifice of vital organs.