Unusual site for metastatic renal cell carcinoma – A case report

Introduction. The most common malignant tumor of the kidney is renal cell carcinoma (> 90%). The metastasis of the renal cell carcinoma in lingual base is very rare. Case report. Patient, 74 years old, renal cell carcinoma underwent radical nephrectomy with evacuation of regional lymph nodes and without any further therapy. After two years of disease-free period, patient appeared with the symptom of difficult swallowing. Ultrasound showed tumor spreading in number of organs. Histopathological analysis of tissue from lingual base confirmed metastatic tumor. Conclusion. After radical surgical treatment of the malignant disease, it is important to examine multiple organ systems. Appropriate approach to the diagnostics and evaluation the entire condition of the patient in this stage of the disease, especially lingual base can relieve patients discomfort and provide prolonged survival, even if the prognosis is unfavourable.


INTRODUCTION
Renal cell carcinoma (RCC) is neoplasia that originates from the epithelium of the renal tubules [1].
Both genders are affected, but it is more common in men from industrialized regions.
Incidence of RCC increases after 40 years and declines after 75 years old.Tobaco smoking is major risk factor beside exposure to arsenic compounds and other cancerogenes (organic solvents, pesticides etc).Hematuria, pain and weight loss are first simptoms of the disease.
Grossly, tumour is surrounded with capsule, within cortex of the kidney.The average size is about 7 cm, with intense yellow-golden color on cut surface (lipid content in cells), with areas of cystic degeneration, focuses of necrosis, haemorrhagia and calcificationes [1].Surgical procedure in smaller tumours is more often nephron-sparing tretman.
Most frequently histological variants of renal cell carcinomas are: clear cell, papillary, chromophobe, medullary, mucinous.Histologicaly, clear cell RCC may have several architectural structures: solitary, alveolar, acinar.Tumour cells are clear in appearance with eosinophilic cytoplasma and scanty vascular stroma.Sometimes shows tubular or pseudopapillay pattern.Nuclei are uniform, round in shape, with finely distribution of chromatin [1].
Immunohistochemistry could be of a great help in distiction of tumour tissue that is positive for low molecular weight cytokeratines CK8/18, Cam 5.2, vimentine, RCC and EMA [1].After the stage itself, most important prognostic parameter in nuclear grade.
Acording to the Fuhrman grading system, Grade 1 has small hyperchromatic nuclei, without nucleoli.Grade 2 has finely granular chromatin, but incospicious nucleoli.For nuclear grade 3, nucleoli are easily recognizable and grade 4 is caracterized by nuclear pleomorphism, hyperchromasia and single to multiple macronucleoli [1].About 50% of RCC are at stage 1 or 2, less than 5% are stage 4. Hematogenous metastases are most common to the lung, also lymphatic and retrograde metastasis.Prognosis is most accurately predicted by stage and nuclear grade [1].
Usual sites of metastatic RCC are: lung, bone, liver and brain, even after 10 years [2,3].Ultrasound is first diagnostic tool to determine the stage of the disease combined with abdominal CT [1].The metastasis of the renal cell carcinoma in lingual base is very rare.

CASE REPORT
In April 2014, a 74 years old patient reported to our center with signs of painless haematuria.After diagnostic procedures he went radical nephrectomy of the left kidney, with removing preaortical and paraaortical lymph nodes.Pathology report confirmed well demarcated tumour 6,5 × 5,5 × 4 cm sized, situated at apical pole of the kidney.Tumour tissue is clear cell carcinoma composed of clear and granular cells with hiperchromatic nuclei and visible nucleoli (Figures 1. and 2.).Nuclear grade by Fuhrman was 2. Foci of necrosis and haemorrhage were present.Margines were free from tumour.Tumour cells reacted positively for: RCC (Figure 3.), CD10, AMACR, but negative for CK7.Hilar region contained 2 positive lymph nodes (Figures 4. and 5.), but 4 were negative.The group of preaortal and paraaortal lymph nodes contained 1 positive lymph node, and 3 negative nodes -T1b N1 M0 [4].The patient was not given any other treatment but surgical (nephrectomy).He did not come at any scheduled medical examination, but two years later the patient referred to ORL department complaining to difficulties in swallowing that lasts for several months, in March 2016.He underwent CT of the chest and abdomen with contrast that revealed bilateral metastatic deposits in lungs and also nectrotizing formations in mediastinum, metastatic deposits in thyreoidea, liver, both iliac bones and a lingual base tumour.Palliative operative treatment of a mass in lingual base was done and the current pathology report resulted by tumour tissue composed of large clear cells with eosinophilic cytoplasma in ulcerated mucosa (Figures 6-9.), that expresses positivity for RCC (Figures 10. and 11.) and represent metastasis of the previously diagnosed kidney tumour.Although, metastasectomy is the method of choice in cases like this, inoperable generalised metastatic disease was radiologically proven.The following control physical examination was sheduled for a month, but the patient died 20 days after the hospital's release.

DISCUSSION
Lingual base is the site of many benign tumours and pseudotumours.The most common malignant tumour in oral cavity is planocellular carcinoma (90%).The lingual base itself is in 50% the most common site for primary planocellular carcinoma.In majority cases lingual tumours show exophytic growth with ulcearation on surface.With progressive growth tumours become indurated and develop raised and everted margins.
Even clinically small tumours infiltrate deeply into the muscle.Infiltration of the lingual musculature may cause pain, dysphagia and dysphonia [5].About 1% of all oral cancers are metastases of primary tumours elsewhere in the body, and they are located in the soft tissues (gingiva and tongue), bones (mandible or maxilla).Any malignant tumour can metastase in oral cavity, but the most common reported are malignancies of lung, liver, prostate and breast.The soft tissue metastases manifest as haemorrhagic tumours with ulceration, rapidly evolving.Despite the fact that oral tumours often give symptoms that can easily been seen, many of them represent advanced disease, that require mutilant treatment and implicate a poor prognosis.In most patients with oral metastasis, the primary tumour has already been diagnosed and treated.Sometimes, existance of oral metastasis leads to detection of metastases elsewhere in the body, so the treatment is restricted (palliative).Prognosis is poor, and median survival is less than 6 months [2,6,7,8].
Lingual base is common localisation for primary planocellular carcinoma, but is unusual site for metatstic renal cell carcinoma.Oral metastasis represent spreding of the malignant tumour which already had metastased in distant localisations.However, metastases to the oral cavity are in 30% of cases the first indication of an otherwise occult malignancy.Online First April, 2018.