Background

Locally advanced head and neck cancer is one of the major oncological problems in India. Despite significant advances in treatment delivery techniques in recent years, loco-regional failure following concurrent chemo-radiotherapy persists. Failure in the form of residual and recurrent disease within the high-dose region is the most common location, followed by marginal treatment failure. Isolated cutaneous nodules had never been mentioned in any previous literature, especially during concurrent chemoradiotherapy.

Case presentation

A 51-year-old chronic smoker male presented to radiation oncology OPD 8 months back with a complaint of gradually progressive swelling in the left side of his neck near the mastoid region with occasional foreign body sensation while swallowing followed by new onset otalgia and restricted mouth opening.

On examination, the patient was normally built and on local examination had an induration of about 2×2cm in the left tonsillar fossa with involvement of the anterior tonsillar pillar. There was multiple hard, non-tender, matted lymph node present at bilateral level II; left levels III, IV, and V levels. Biopsy from tonsillar lesion reported moderately differentiated squamous cell carcinoma and staged as locally advanced oropharyngeal cancer with TNM staging of cT4aN2cM0 (Group stage – IVB). Due to the very high burden of the disease, we had planned a whole body PET-CT scan for assessment of disease status. The whole body PET-CT scan reported an FDG avid soft tissue density lesion at the left tonsil, of 1.4 × 1.5 cm (SUV-max – 17.8) with multiple FDG avid cervical lymphnodes at levels II, III, IV, and V and supraclavicular fossa, largest of 3.4 × 3.5 cm (SUV-max of 17.3) at level III. Due to the very large nodal burden, we planned induction chemotherapy followed by definitive chemoradiotherapy.

After 4 cycles of 3 weekly Carboplatin (AUC – 5) and Paclitaxel (175mg/m2)-based chemotherapy, he had a good clinicoradiological response. The patient was planned for definitive Chemo-RT- with 69.96Gy and 59.4Gy in 33 fractions for gross disease and prophylactic volume in 6.5 weeks with 5 cycles of concurrent cisplatin-based chemotherapy. After the 23rd fraction, it was observed that there was a small skin nodule just above the sternoclavicular junction which was within 59.4Gy volume (Figs. 1 and 2). Fine needle aspiration cytology confirmed the diagnosis of metastatic carcinoma (Fig. 3). The radiation dose received by that region was calculated so he was further planned to receive 10Gy/5# by an electron to the skin nodule. The patient was on regular follow-up.

Fig. 1
figure 1

Colorwash showing 95% dose prescription to IPC_IR volume (purple) with metastatic skin module (white)

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Fig. 2
figure 2

DVH showing a graphical representation of PTV_HR volume (66Gy) (red), PTV_IR volume (60Gy) (purple), and metastatic skin nodule (white)

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Fig. 3
figure 3

FNAC from skin nodule s/o metastatic squamous cell carcinoma

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There was a clinical (Fig. 4) and radiological progression (Fig. 5) of this skin nodule in the PET CT scan done at 3 months post-treatment. Whole body PET-CT scan was suggestive of non-FDG avid tissue density at the left tonsillar fossa with metabolically active level IB, II, III, and IV lymph node, the largest at level III 1.8 × 1.9cm (SUV max – 7) which was previously 3.5 × 3.4cm (SUV-max – 17.3) in diameter and small nodular skin deposit of 1.1×0.9cm (SUV-max – 5.6). He received 4 cycles of Gemcitabine (1000mg/m2 on day 1 and day 8) with Carboplatin (AUC – 5 on Day 1)-based palliative chemotherapy. On clinical examination, there was one 1 × 1cm hard mobile lymph node present at the left level III cervical region without any significant clinical findings in the head and neck region. Response assessment CT scan of the head, neck, and thorax was suggestive of subcentimetric multiple lymph node in the bilateral cervical region likely inflammatory with no tonsillar lesion. He was further planned for 4 more cycles of chemotherapy. Unfortunately, the patient was reluctant to take further chemotherapy and lost to follow-up after that.

Fig. 4
figure 4

WB PET CT showing FDG avid metastatic skin nodule (white) at right level IV

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Fig. 5
figure 5

Clinical picture of a metastatic skin nodule

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Discussion

The incidence of metastatic skin deposits from head and neck cancers is less than 1%, [1] and it is most commonly seen in laryngeal cancer [2]. Cutaneous deposits from head and neck cancers can be discrete and single, or they may present as multiple nodules at different anatomic sites.

Cases of cutaneous metastasis following definitive chemoradiotherapy had previously been described. After a 1½-year follow-up, Rastogi et al. described a case of the base of the tongue primary with multiple skin nodules [3]. Longo et al. also mentioned a case of oral tongue skin deposit after a long follow-up [4]. Tashnin et al. reported a case of the oropharynx with failure of the facial skin 1 month after the completion of chemoradiotherapy [5]. But it has never been described within the radiation treatment field during the treatment of an oropharyngeal squamous cell cancer patient.

Treatment failure is most common in the form of residual and recurrent disease in the high-dose region or “infield failures.” [6] Marginal and out-of-field failures are usually rare and occur after the completion of treatment. A dermal deposit in the form of marginal failure before the completion of radiotherapy has not been reported yet. The usual mode of skin metastasis is by hematogenous spread, which is why patients with skin metastases usually present with lung and bone metastases [7]. Our case is the first to describe a cutaneous deposit during the treatment of head and neck squamous cell carcinoma. This condition can only be explained by the presence of occult skin metastasis through the lymphatic spread, which was in a subclinical state at the time of treatment. This case demonstrates the significance of a weekly, detailed clinical examination for tumor response and toxicity assessment, as well as the possibility of skin involvement via lymphatic spread in a disease with a high nodal burden.

Skin metastasis from head and neck cancer has a very grave prognosis, with a mean survival of 4 months or less [4]. Up to this point, all of the previously described cases were treated with palliative chemotherapy because they had concurrent systemic metastasis with their skin nodule and were poor responders to palliative chemotherapy. In the present case, we treated the patient with an electron boost after the completion of radiotherapy followed by palliative chemotherapy, and after 7 months since the appearance of the skin nodule, the patient was alive and disease-free.

Conclusion

During the course of definitive chemoradiotherapy, a cutaneous deposit from oropharyngeal squamous carcinoma within the radiotherapy treatment field is quite uncommon. In our situation, occult skin spread through the lymphatics was likely present from the beginning of the treatment or while it was being administered and only became visible in between radiotherapy treatments. In a radiation therapy field, a new skin nodule could seem benign, but we should nevertheless constantly analyse it with FNAC. Early detection in these cases enables an aggressive approach that can halt the disease’s spread.